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authorKees Cook <keescook@chromium.org>2013-11-12 15:11:17 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-11-29 10:42:17 -0800
commit4004afd5f51ad0a86be405522b1ecf28ba66f4e5 (patch)
tree4cb10f0eeb16122cdb0b0b658de66aacab4d3d12
parent4d290883942593c37e79f66d7ba69f329b0ad9d4 (diff)
exec/ptrace: fix get_dumpable() incorrect tests
commit d049f74f2dbe71354d43d393ac3a188947811348 upstream. The get_dumpable() return value is not boolean. Most users of the function actually want to be testing for non-SUID_DUMP_USER(1) rather than SUID_DUMP_DISABLE(0). The SUID_DUMP_ROOT(2) is also considered a protected state. Almost all places did this correctly, excepting the two places fixed in this patch. Wrong logic: if (dumpable == SUID_DUMP_DISABLE) { /* be protective */ } or if (dumpable == 0) { /* be protective */ } or if (!dumpable) { /* be protective */ } Correct logic: if (dumpable != SUID_DUMP_USER) { /* be protective */ } or if (dumpable != 1) { /* be protective */ } Without this patch, if the system had set the sysctl fs/suid_dumpable=2, a user was able to ptrace attach to processes that had dropped privileges to that user. (This may have been partially mitigated if Yama was enabled.) The macros have been moved into the file that declares get/set_dumpable(), which means things like the ia64 code can see them too. CVE-2013-2929 Reported-by: Vasily Kulikov <segoon@openwall.com> Signed-off-by: Kees Cook <keescook@chromium.org> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/ia64/include/asm/processor.h2
-rw-r--r--fs/exec.c6
-rw-r--r--include/linux/binfmts.h3
-rw-r--r--include/linux/sched.h4
-rw-r--r--kernel/ptrace.c3
5 files changed, 13 insertions, 5 deletions
diff --git a/arch/ia64/include/asm/processor.h b/arch/ia64/include/asm/processor.h
index e0a899a1a8a6..5a84b3a50741 100644
--- a/arch/ia64/include/asm/processor.h
+++ b/arch/ia64/include/asm/processor.h
@@ -319,7 +319,7 @@ struct thread_struct {
regs->loadrs = 0; \
regs->r8 = get_dumpable(current->mm); /* set "don't zap registers" flag */ \
regs->r12 = new_sp - 16; /* allocate 16 byte scratch area */ \
- if (unlikely(!get_dumpable(current->mm))) { \
+ if (unlikely(get_dumpable(current->mm) != SUID_DUMP_USER)) { \
/* \
* Zap scratch regs to avoid leaking bits between processes with different \
* uid/privileges. \
diff --git a/fs/exec.c b/fs/exec.c
index fd774c7cb483..e72f6bbbde2e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1670,6 +1670,12 @@ int __get_dumpable(unsigned long mm_flags)
return (ret > SUID_DUMP_USER) ? SUID_DUMP_ROOT : ret;
}
+/*
+ * This returns the actual value of the suid_dumpable flag. For things
+ * that are using this for checking for privilege transitions, it must
+ * test against SUID_DUMP_USER rather than treating it as a boolean
+ * value.
+ */
int get_dumpable(struct mm_struct *mm)
{
return __get_dumpable(mm->flags);
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 70cf138690e9..df97ca4aae52 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -99,9 +99,6 @@ extern void setup_new_exec(struct linux_binprm * bprm);
extern void would_dump(struct linux_binprm *, struct file *);
extern int suid_dumpable;
-#define SUID_DUMP_DISABLE 0 /* No setuid dumping */
-#define SUID_DUMP_USER 1 /* Dump as user of process */
-#define SUID_DUMP_ROOT 2 /* Dump as root */
/* Stack area protections */
#define EXSTACK_DEFAULT 0 /* Whatever the arch defaults to */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 64803940fa55..e057ea09c851 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -330,6 +330,10 @@ static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
extern void set_dumpable(struct mm_struct *mm, int value);
extern int get_dumpable(struct mm_struct *mm);
+#define SUID_DUMP_DISABLE 0 /* No setuid dumping */
+#define SUID_DUMP_USER 1 /* Dump as user of process */
+#define SUID_DUMP_ROOT 2 /* Dump as root */
+
/* mm flags */
/* dumpable bits */
#define MMF_DUMPABLE 0 /* core dump is permitted */
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index a146ee327f6a..cf021a03019c 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -257,7 +257,8 @@ ok:
if (task->mm)
dumpable = get_dumpable(task->mm);
rcu_read_lock();
- if (!dumpable && !ptrace_has_cap(__task_cred(task)->user_ns, mode)) {
+ if (dumpable != SUID_DUMP_USER &&
+ !ptrace_has_cap(__task_cred(task)->user_ns, mode)) {
rcu_read_unlock();
return -EPERM;
}